The subject matter disclosed herein relates to measuring material thickness using ultrasonic transducers and in one embodiment to a piezoelectric sensing device that comprises a flexible circuit for use in high temperature environments.
Several industries (e.g., oil and gas, refinery, chemical, power generation) require the transport of fluid (e.g., liquids or gases) through pipes. Nondestructive testing systems can be placed on the outer surface of these pipes to monitor corrosion/erosion of the pipes, including corrosion/erosion on the interior of pipe walls. These systems are usually implemented as part of manual inspection over the course of time, wherein the pipe wall thickness and changes in the thickness are monitored over time. In some cases, the probe or other nondestructive testing device is permanently coupled to the outer surface of the pipe to continuously monitor corrosion/erosion at that location to determine pipe corrosion/erosion rates and to determine whether that pipe location is in need of preventative maintenance to prevent a pipe failure.
One example of a nondestructive testing system used to monitor corrosion/erosion of a pipe is an ultrasonic testing system. When conducting ultrasonic testing of a pipe, an ultrasonic pulse is emitted from a probe coupled to the outer surface of the pipe and passed through the pipe wall. As the ultrasonic pulse passes into and through the pipe wall, various pulse reflections called echoes are reflected back to the probe as the pulse interacts with the outer surface of the pipe, internal structures within the pipe wall, and with the back wall of the pipe wall. The echo signals can be displayed on a screen with echo amplitudes appearing as vertical traces and time of flight or distance as horizontal traces. By tracking the time difference between the transmission of the ultrasonic pulse and the receipt of the echoes, various characteristics of the pipe can be determined, including pipe wall thickness. If the thickness of the pipe wall at the location of the ultrasonic testing system decreases over time (e.g., as would be shown be a reduction in the time of flight of the back wall echo), this can be an indication of corrosion/erosion.
Various factors influence the configuration of devices and in particular the materials for use in these non-destructive testing systems. Operating conditions such as the operating temperature in some applications, for example, can exceed the temperature thresholds of materials such as copolymers of polyvinylidene fluoride (PVDF) (e.g., P(VDF-TrFE)) or polytetrafluoroethylene (PTFE)). Processing conditions including temperatures related to certain processing steps during manufacture are also limiting. Performance factors such as accuracy and sensitivity to small defects and to small changes in material thickness are other factors that preclude the use of particular materials and combinations thereof. However, while improved performance can be achieved using certain configurations of materials, these configurations often result in physical characteristics (e.g., height profile) that limit the applicability of the resultant devices in certain applications, including high temperature applications (e.g., nuclear power generation environments which are routinely operating well above 120° C.).
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.